refactor: establish Catalog component directory structure for PolicyWorkbench

Create new organized structure for PolicyWorkbench refactoring:
- Catalog/ directory with components/, composables/ subdirectories
- Copy Catalog.vue (from RealPolicyWorkbench.vue) as root orchestrator
- Copy PolicyRuleCard.vue and PolicyRuleEditorPanel.vue to components/
- Copy useRealPolicyWorkbench.ts to composables/
- Add README.md documenting refactoring plan and phases

This is Phase 1 (base structure) of planned multi-phase refactoring to:
- Extract usable composables (useNavigation, useCatalogState)
- Break monolithic 4095-line component into modular pieces (~200-400 lines each)
- Improve maintainability and testability

Original files remain in place during transition period.

Signed-off-by: Vitor Mattos <[email protected]>

Author: vitormattos